Gelatinous enhancer for inflator

ABSTRACT

The present invention relates to a gelatinous enhancer for an inflator, including silicone oil and ammonium nitrate.

This nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2007-319125 filed in Japan on 11 Dec. 2007, which is incorporated by reference.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to a gelatinous enhancer for an inflator, which is used in an inflator for an air bag apparatus or other applications.

2. Description of Arts

B/KNO₃ is widely employed as a enhancer for an inflator. B/KNO₃ has a high combustion temperature and favorable ignitability in relation to a gas generant. However, B/KNO₃ burns vigorously, and therefore burns out instantaneously. Hence, B/KNO₃ is insufficient as a enhancer for a gas generant having low ignitability. Furthermore, B/KNO₃ is expensive and exhibits a low gas efficiency.

Further, when E/KNO₃ is used, a problem arises in that an abnormal noise occurs during an operation. This problem can be solved by employing a elastic enhancer, but an elastic enhancer is easily affected by the environmental temperature and is therefore unsatisfactory in terms of operational reliability over a wide temperature range (−40° C. to 105° C.). US-A No. 2005/0235863, JP-A No. 2000-8637 and JP-A No. 2002-12493 are in the state of arts.

SUMMARY OF INVENTION

An invention relates to a gelatinous enhancer for an inflator, including silicone oil and ammonium nitrate.

DETAILED DESCRIPTION OF INVENTION

The present invention provides a gelatinous enhancer for an inflator, which can solve problems relating to costs, ignitability in relation to a gas generant, and so on.

The invention preferably relates to a gelatinous enhancer for an inflator, wherein the silicone oil content ranges from 5 to 35 mass % and the ammonium nitrate content ranges from 65 to 95 mass %.

The gelatinous enhancer for an inflator according to the present invention generates more combustion heat than B/KNO₃, which is widely used as a enhancer, and therefore exhibits favorable ignitability in relation to a gas generant having low ignitability. Further, the gas efficiency of the gelatinous enhancer for an inflator according to the present invention is high, and therefore gas generated thereby can be used also to inflate an air bag. Thus, gas generated from the gas generant can be complemented by the gas generated by the gelatinous enhancer.

PREFERRED EMBODIMENT OF INVENTION

Known silicone oil is used in the present invention (see [0016] to [0019] of US-A No. 2005/0235863, for example), and either straight silicone oil or denatured silicone oil may be used. However, straight silicone oil (polydimethylsiloxane, for example) is preferable.

To provide the enhancer in a gelatinous form, the viscosity of the silicone oil is preferably within a range of 100 to 20,000 cm²/s, more preferably within a range of 500 to 15,000 cm²/s, and even more preferably within a range of 1000 to 15,000 cm²/s. The method of measuring the viscosity corresponds to the method described in JIS K2283, and a value measured at 25° C. is taken.

The silicone oil content is preferably between 3 and 30 mass %, more preferably between 5 and 25 mass %, and even more preferably between 5 and 20 mass %.

Ammonium nitrate used in the present invention may be a normal ammonium nitrate or an ammonium nitrate subjected to phase stabilization by a known method (for example, JP-A No. 2002-338241, JP-A No. 2006-520312, JP-A No. 10-259085) using potassium nitrate, an inorganic potassium salt such as potassium perchlorate, an organic potassium salt such as potassium oxalate, or the like.

The ammonium nitrate content is preferably between 70 and 97 mass %, more preferably between 75 and 95 mass %, and even more preferably between 80 and 95 mass %.

The gelatinous enhancer for an inflator according to the present invention may be a three component-based enhancer including a nitrogen-containing compound in addition to the silicone oil and ammonium nitrate described above. When a nitrogen-containing compound is included, the gas efficiency (mol/100 g; expressing the number of moles of gas generated per 100 g of gas generant) increases and an initial pressure upon ignition increases, preferably leading to an improvement in ignitability in relation to the gas generant.

When a nitrogen-containing compound is included, the nitrogen-containing compound content is preferably 30 mass % or less of the total amount of the ammonium nitrate and the nitrogen-containing compound.

The nitrogen-containing compound may be selected from a tetrazole derivative, guanidine, guanidine carbonate, nitroguanidine, dicyandiamide, nitroaminoguanidine, and nitroaminoguanidine nitrate.

Examples of tetrazole derivatives include tetrazole, 5-aminotetrazole, 5,5′-bi-1H-tetrazole, 5-nitroaminotetrazole, 5-aminotetrazole zinc salt, 5-aminotetrazole copper salt, bitetrazole, bitetrazole potassium salt, bitetrazole sodium salt, bitetrazole magnesium salt, bitetrazole calcium salt, bitetrazole diammonium salt, bitetrazole copper salt, and bitetrazole melamine salt.

The gelatinous enhancer for an inflator according to the present invention can be obtained by blending a predetermined amount of silicone oil, a predetermined amount of ammonium nitrate, and in certain cases, a predetermined amount of a nitrogen-containing compound.

The gelatinous enhancer for an inflator according to the present invention can be applied to various types of inflators having a known gas generant, for example an inflator for an air bag used in a driver side, an inflator for an air bag for a front passenger side, an inflator for a side air bag, an inflator for an inflatable curtain, an inflator for a knee bolster, an inflator for an inflatable seatbelt, an inflator for a tubular system, and an inflator for a pretensioner of various types of vehicles.

EXAMPLES Examples and Comparative Example

By blending the components shown in Table 1, a gelatinous enhancer for an inflator according to Examples and a enhancer according to Comparative Example were obtained. The following tests were performed on these enhancers. The results are shown in Table 1.

(1) Combustion Temperature (K)

A simulation value based on a thermochemical equilibrium calculation program.

(2) Combustion Heat (cal/g)

A simulation value based on a thermochemical equilibrium calculation program.

(3) Gas Efficiency (mol/100 g)

A simulation value based on a thermochemical equilibrium calculation program.

(4) Friction Sensitivity (N), Drop Hammer Sensitivity (cm)

The friction sensitivity (N) and the drop hammer sensitivity (cm) were measured on the basis of an explosive performance test method described in JIS K4810-1979.

TABLE 1 Drop Combustion Friction hammer temperature Combustion Gas efficiency sensitivity sensitivity Gas generant composition (mass %) (K) heat (cal/g) (mol/100 g) (N) (cm) Example 1 Silicone oil(1)/Ammonium nitrate = 10.4/89.6 2393 1191 4.06 >353 50-60 Example 2 Silicone oil(2)/Ammonium nitrate = 10.4/89.6 2393 1191 4.06 >353 50-60 Example 3 Silicone oil(3)/Ammonium nitrate = 10.4/89.6 2393 1191 4.06 >353 50-60 Comparative B/KNO₃ = 25/75 3089 827 1.34 >353 30-40 Example 1

-   Ammonium nitrate: product name K-320 (manufactured by Sumitomo     Chemical Co., Ltd.) -   Silicone oil (1): product name TSF451-30M (manufactured by Momentive     Performance Materials Japan LLC.), viscosity 3000 cm²/s -   Silicone oil (2): product name KF-96 (manufactured by Shin-Etsu     Chemicals Co., Ltd.), viscosity 5,000 cm²/s -   Silicone oil (3): product name KF-96H (manufactured by Shin-Etsu     Chemicals Co., Ltd.), viscosity 10,000 cm²/s 

1. A gelatinous enhancer for an inflator, comprising silicone oil and ammonium nitrate.
 2. The gelatinous enhancer according to claim 1, wherein the silicone oil content ranges from 5 to 35 mass % and the ammonium nitrate content ranges from 65 to 95 mass %. 